ESD protection devices of the kind mentioned in the opening paragraph are known, for example from a Philips product data sheet of the PESDxL2BT series (Rev. 01—1 Nov. 2005), “Low capacitance double bidirectional ESD protection diodes in SOT23”. This datasheet discloses a low capacitance double bidirectional Electrostatic Discharge (ESD) protection diodes in a SOT23 small Surface Mounted Device (SMD) plastic package designed to protect two signal lines from the damage caused by ESD and other transients. The package comprises three pins (“cathode 1”, “cathode 2”, “double cathode 3”). Between pins “cathode 1” and “double cathode 3” there is a first anti-series connection of two Zener-diodes, and between pins “cathode 2” and “double cathode 3” there is a second anti-series connection of two Zener-diodes. The data sheet also discloses (in FIG. 8 of the data sheet) the voltage-current characteristic of the ESD protection diodes. The voltage-current characteristic clearly shows a sharp current increase after that the breakdown voltage (VBR) has been reached. The data sheet discloses (see table 8 of the data sheet) different ESD protection device types having a breakdown voltage (max value) between 6.9V and 30.3V. The corresponding clamping voltages are lying between 8V and 70V depending on the ESD structure type.
A disadvantage of the known ESD protection devices is that the clamping voltage is still relatively high.